1. Field of the Invention
A process for producing vinegar and, more in particular, it relates to a process for producing vinegar capable of selectively removing iso-valeric acid contained as a smelly component in vinegar thereby obtaining vinegar of favorable flavor by using a non-ionic porous synthetic absordent.
2. Description of the Prior Art
Activated carbon has been utilized for controlling the flavor of vinegar and there has been employed a method of putting activated carbon into vinegar to be processed, stirring and then separating activated carbon by filtration. In addition, it has also been proposed a process of removing iso-valeric acid as a smelly component in vinegar by passing vinegar prepared from corn as starting material through an activated carbon layer having a thickness of not less than 1cm (refer to Japanese Patent Application No. 30776/1989).
By the way, non-ionic porous synthetic adsorbents have been utilized so far only to the separation and purification of physiologically active substance as described in, for example, Janpanese Patent Publication No. 17833/1979 (collecting and purifying process for cephalosporin C) or Japanese Patent Publication No. 6917/1982 (production process for an aqueous solution of adenosine triphosphate at high purity).
Since vinegar used for processing foodstuffs has been used in a wide range for various foodstuffs, it has highly been demanded for removing those ingredients giving undesired effects on flavors of foodstuffs. Vinegar is prepared by alcohol fermentation and then acetic acid fermentation of cereals, fruits or sugars as starting materials and vinegar prepared in this way usually contains uncomfortable smelly components. Then, activated carbon has been used for removing iso-valeric acid as the uncomforatable smelly components.
However, the method of putting activated carbon in vinegar, stirring and then separate active carbon filtration requires a great amount of activated carbon. For instance, activated carbon as much as 25-30 g/l is required for reducing the content of iso-valeric acid in vinegar from 50 ppm to less than 10 ppm, which brings about problems, for example, increased production cost or extremely poor operation efficiency.
Further, vinegar starting from cereals, fruits or sugars has enriched favorable flavor or useful ingredients derived from the starting material. However, if the method of utilizing activated carbon is applied to vinegar, although iso-valeric acid as the uncomfortable nasty components can be removed, inherent flavors or colors derived from starting material such as fruits are removed together.
Further, since organic acids in vinegar are also removed, vinegar of strong sourness only composed of acetic acid is formed. After all, the method of using activated carbon involves a problem that inherent flavors, colors and taste derived from cereals, etc. as the starting material are lost to always produce only tasteless and odorless vinegar with no particular feature.
In a case if the treatment with activated carbon is applied to vinegar to such as extent as not reducing the flavor or color inherent to the starting material, iso-valeric acid remains by 10 ppm or more and the resultant vinegar shows uncomfortable malodor to give undesired effects or foodstuffs.